The present invention relates to an accident-prevention device for buildings, particularly for assembling prefabricated components made of concrete or the like, which are designed to provide individual protection against falls of workers assigned to walking high above ground level on buildings being erected.
Such devices generally comprise a plurality of spaced metal poles which are connected, at their base, to a horizontal surface of the building, formed for example by a beam, and have, at their tip or in an intermediate region of their vertical extension, a passage for a cable which is fixed to the building at its ends and is tensioned by means of appropriate cable tensioning elements so as to form a safety parapet.
In these devices, the poles are designed only to keep the cable at a preset height so that it can be easily engaged by the spring-catches with which the safety belts or harnesses worn by workers are equipped.
In some accident-prevention devices, the poles are inserted in a cavity which is formed inside a concrete component of the building.
In other devices, the poles are provided with a threaded base which can be engaged in a female thread formed inside a bushing which is embedded beforehand into the concrete component.
In other devices, the poles are rigidly coupled to the concrete component by a bayonet coupling, such as for example the device disclosed in U.S. Pat. No. 4,045,003.
In these devices, the load-bearing function is mainly performed by the cable, which discharges the stresses produced by a fall of the worker mainly onto the building to which it is coupled at its ends.
The need to couple the ends of the cable to the building entails the problem of having, on the building, regions that cannot be protected, i.e., the regions that lie between the end poles of the row of poles and the region where the cable is anchored to the building, which is usually located on the same surface that supports the poles. In these regions the cable, by following an inclined path from the tip of the end pole to the surface that supports the poles, cannot be used as a fastening for safety harnesses or belts.
In some devices, the ends of the cable, instead of being anchored directly to the building, are anchored to the end poles. In this case, since they must withstand higher stresses, the end poles are provided with lateral supports or have a structure which is considerably bulkier than the other poles and in practice prevent access to the region of the building located in the immediate vicinity, in any case reducing the length of the cable that can actually be used as a fastening for safety belts or harnesses.
Many conventional safety devices have shock absorbers designed to reduce the peaks of the stresses discharged onto the cable and, by reaction, onto the worker when he falls.
The shock absorbers are usually constituted by springs arranged along the cable or between the cable and a pole or between the cable and the element for anchoring one end of the cable to the building.
Although these shock absorbers reduce the peaks of the stresses discharged onto the worker and onto the cable, they have a limited effect in reducing the peaks of the stresses discharged onto the end poles in a direction which is substantially transverse to the axis of the poles, if the cable is connected to said end poles with its ends.
Because of this, despite the presence of the shock absorbers, the end poles must be either provided with lateral supports, generating the above described problems, or oversized, with consequent cost increases.
The aim of the present invention is to solve the above problems, by providing an accident-prevention device for buildings, particularly for assembling prefabricated components made of concrete or the like, which allows to significantly reduce the stresses transmitted from the cable to the pole transversely to the axis of the pole, thereby avoiding or at least limiting the need to oversize the poles.
Within the scope of this aim, an object of the invention is to provide a device which allows to distribute over a plurality of poles the stresses that are transmitted along the cable, thus reducing the stresses discharged onto each pole.
Another object of the invention is to provide a device which also significantly reduces the peaks of the stresses which, by reaction, are transmitted to the user in case of a fall.
Another object of the invention is to provide a device which allows to protect substantially all the area of a building to which it is applied.
Another object of the invention is to provide a device which allows to arrange the cable even along a path having one or more lateral changes of direction.
Another object of the present invention is to provide a device which is highly reliable and can be manufactured at competitive costs.
These and other objects which will become better apparent hereinafter are achieved by an accident-prevention device for buildings, particularly for assembling prefabricated components made of concrete, which comprises at least one pole and means for detachably connecting a base of said pole to a surface of a building; said pole having, proximate to a tip thereof, guiding means for a cable element which forms a safety parapet, characterized in that said guiding means are adapted to divert, in a direction substantially parallel to the axis of said pole, at least part of the stresses transmitted from said cable element to said pole, and in that said pole is provided with means for cushioning the stresses transmitted from said cable element to said pole in a direction which is substantially parallel to the axis of the pole.